冬小麦冠层温度对大气温度的时滞效应与影响因素研究

冠气温差能够间接监测作物水分变化规律,而冠层温度与大气温度之间存在的时滞效应会影响监测效果,为探明两者之间的时滞效应变化规律及影响因素,本研究以拔节期至乳熟期的冬小麦为研究对象,利用红外温度传感器连续监测灌溉上限分别为田间持水率的95%(T1)、80%(T2)、65%(T3)和50%(T4)4个不同灌溉处理的冠层温度,并同步获取短波净辐射(Short-wave net radiation,R_S)、大气温度(Atmospheric temperature,T_A)、相对湿度(Relative humidity,R_H)等气象数据。利用错位相关法计算冠层温度与大气温度之间的时滞时间(Time lag,T_L),分析其在不同生育期和不同灌溉条件下变化规律,并采用相关性分析法探究气象因子(R_S、T_A、R_H)变化率和日均值与时滞时间的相关性,最后通过通径分析探讨气象因子(R_S、T_A、R_H

Time Lag Effect between Winter Wheat Canopy Temperature and Atmospheric Temperature and Its Influencing Factors

Canopy-air temperature difference can indirectly monitor the variation of crop moisture, and the time lag effect between canopy temperature and atmospheric temperature will affect the monitoring effect. In order to explore the characteristics and influencing factors of the time lag effect between canopy temperature and atmospheric temperature, winter wheat from jointing stage to ripening stage was used as the research object. The infrared temperature sensor was used to continuously monitor the canopy temperature of four different irrigation treatments with irrigation upper limits of 95% (T1), 80% (T2), 65% (T3) and 50% (T4) of field water capacity, and simultaneously obtained meteorological data such as short-wave net radiation (RS), atmospheric temperature (TA) and relative humidity (RH). The time lag between canopy temperature and atmospheric temperature was calculated by dislocation correlation method, and its variation characteristics under different growth stages and different irrigation conditions were analyzed. The correlation analysis method was used to explore the correlation between the change rate and daily mean value of meteorological factors (RS, TA, RH) and time lag. Finally, the common influence of meteorological factors (RS, TA, RH), soil moisture content (SMC) and leaf area index (LAI) on time lag was discussed by path analysis. The results showed that the change of winter wheat canopy temperature was ahead of the atmospheric temperature under different growth stages and different irrigation conditions;under different irrigation treatments, the lag time of T1, T2 and T3 treatments was higher than that of T4 treatment, and the lag time was decreased firstly and then increased at different growth stages. The correlation between the change rate of shortwave net radiation (RSCR), the change rate of atmospheric temperature (TACR) and the change rate of relative humidity (RHCR) and the time lag was higher than that between the corresponding daily mean and the time lag. At the same time, the correlation between RSCR and lag time was the highest (R=0.718~0.806), followed by TACR (R=0.582~0.661) and RHCR (R=-0.534~-0.570). Path analysis showed that the lag time was mainly affected by RSCR, SMC and LAI, but the main factors affecting the lag time were different under different irrigation conditions. T1, T2 and T3 treatments were mainly affected by RSCR and LAI, while T4 was mainly affected by RSCR and SMC. The research result can provide a theoretical basis for monitoring crop water changes by using canopy temperature difference information.